1. Field of the Invention
This present invention relates to the secure storage of metadata, in particular security related metadata required for decryption or encryption of data such as media content in the form of audio or video data, or the like.
2. Description of the Related Art
The delivery, storage and use of digital data often needs to be controlled so that only authorized recipients may use that data in given ways. This field is Digital Rights Management (DRM) and typically operates by maintaining the data in encrypted form, as far as possible, and to restrict the dissemination of the appropriate “keys” to decrypt the data. Such encrypted data is typically audio or video data and may be referred to as “content” data. The associated data containing instructions (such as keys) on how the content data may be decrypted may be referred to as “metadata”. In the example of pay-TV the metadata is broadcast as encrypted control words.
In systems in which content data is received from a broadcast stream, stored, processed to be used (e.g., viewed for video, listen to audio) or distributed to other devices, the content data is typically encrypted using a common encryption scheme. This is because this requires a large bandwidth and it would not be feasible to provide different content data streams to each recipient device. The associated metadata, though, may be encrypted uniquely to each recipient device, as the metadata is a much smaller size.
To maintain security in devices processing content data, the metadata itself is kept in encrypted form until used. At this point, the metadata is decrypted and stored in memory for use by cryptographic processes and any other security related processes such as hardware switches.